Change the curvnet variable from a global const struct vnet *,

previously always pointing to the default vnet context, to a
dynamically changing thread-local one.  The currvnet context
should be set on entry to networking code via CURVNET_SET() macros,
and reverted to previous state via CURVNET_RESTORE().  Recursions
on curvnet are permitted, though strongly discuouraged.

This change should have no functional impact on nooptions VIMAGE
kernel builds, where CURVNET_* macros expand to whitespace.

The curthread->td_vnet (aka curvnet) variable's purpose is to be an
indicator of the vnet context in which the current network-related
operation takes place, in case we cannot deduce the current vnet
context from any other source, such as by looking at mbuf's
m->m_pkthdr.rcvif->if_vnet, sockets's so->so_vnet etc.  Moreover, so
far curvnet has turned out to be an invaluable consistency checking
aid: it helps to catch cases when sockets, ifnets or any other
vnet-aware structures may have leaked from one vnet to another.

The exact placement of the CURVNET_SET() / CURVNET_RESTORE() macros
was a result of an empirical iterative process, whith an aim to
reduce recursions on CURVNET_SET() to a minimum, while still reducing
the scope of CURVNET_SET() to networking only operations - the
alternative would be calling CURVNET_SET() on each system call entry.
In general, curvnet has to be set in three typicall cases: when
processing socket-related requests from userspace or from within the
kernel; when processing inbound traffic flowing from device drivers
to upper layers of the networking stack, and when executing
timer-driven networking functions.

This change also introduces a DDB subcommand to show the list of all
vnet instances.

Approved by:	julian (mentor)

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/net/netisr.c b/sys/net/netisr.c
index ed5466c..efbc183 100644
--- a/sys/net/netisr.c
+++ b/sys/net/netisr.c
@@ -43,6 +43,7 @@
 #include <sys/resourcevar.h>
 #include <sys/sysctl.h>
 #include <sys/unistd.h>
+#include <sys/vimage.h>
 #include <machine/atomic.h>
 #include <machine/cpu.h>
 #include <machine/stdarg.h>
@@ -142,7 +143,10 @@ netisr_processqueue(struct netisr *ni)
 		IF_DEQUEUE(ni->ni_queue, m);
 		if (m == NULL)
 			break;
+		VNET_ASSERT(m->m_pkthdr.rcvif != NULL);
+		CURVNET_SET(m->m_pkthdr.rcvif->if_vnet);
 		ni->ni_handler(m);
+		CURVNET_RESTORE();
 	}
 }